Dummy patterns and method for generating dummy patterns

ABSTRACT

A method for generating dummy patterns includes providing a layout region having a layout pattern with a first density, inserting a plurality of first dummy patterns with a second density corresponding to the first density in the layout pattern, dividing the layout region into a plurality of sub-regions with a third density, adjusting a size of the first dummy pattern according to a difference between the second density and the third density, and outputting the layout pattern and the first dummy patterns on a photomask.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to dummy patterns and a method for generatingdummy patterns, and more particularly, to dummy patterns and a methodfor generating dummy patterns used in planarization process.

2. Description of the Prior Art

Along with an increase in speed of semiconductor devices, downsizing andhigher integration of elements, such as transistors and multilevelinterconnects are now in progress. An ever increasing accuracy andprecision for forming circuit layout with higher density on the wafer istherefore required. Of course, those of ordinary skill in the art willeasily recognize that layout with higher density requires better surfaceflatness of the wafer for increasing the accuracy for forming the layoutpattern. Conventionally, chemical mechanical polishing (CMP) process isan effective and important method for wafer planarization. And result ofCMP becomes critical for forming necessary elements. In detail, waferregions with a low pattern density are known to be etched faster thanwafer regions with high pattern density. Thus, for a given etch time, adisproportionately greater amount of material is etched from the lowpattern density regions than the high pattern density regions.Accordingly, thickness in the low pattern density regions is smallerthan that in the high pattern density regions, and thus an unevensurface having film thickness variation, dishing, or erosion isresulted. Besides the thickness variation problem, the uneven surfaceafter CMP process further suffers serious problems such as pattern sizeerror and poor critical size uniformity (CDU). Furthermore, it is foundthat different pattern densities also adversely impact othersemiconductor process such as patterning process or etching process. Forexample, over-etching and/or incomplete etching may be resulted due tothe different pattern densities on one wafer.

As a countermeasure against to the above problems, there have beenproposed a method in which dummy patterns are randomly positioned in thelow pattern density regions. By positioning the dummy patterns in thelow pattern density regions, the pattern density is raised. Accordingly,the approach of inserting dummy patterns between design patterns is nowessential for controlling variations in the flatness of the surface of awafer or a chip.

However, the conventional approach uses dummy patterns with identicalshape and size arranged in an array. Though the dummy patterns alleviatedensity difference between the low pattern density regions and the highpattern density regions, it is no longer competent when the wafer or thechip is formed to have more regions with varied densities due to thecomplexity of the integrated circuit (IC) design. Furthermore, theconventional dummy patterns also suffer from several drawbacks andlimitations such as being irresistible to stress between regions withdifferent pattern densities and increases optical proximity correction(OPC) processing time.

In view of the above, there exists a need for innovative dummy patternsand a smart method for generating dummy patterns.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided amethod for generating dummy patterns. The method includes steps ofproviding a layout region having a layout pattern with a first density,inserting a plurality of first dummy patterns with a second densitycorresponding to the first density in the layout pattern, dividing thelayout region into a plurality of sub-regions with a third density,adjusting a size of the first dummy pattern according to a differencebetween the second density and the third density, and outputting thelayout pattern and the first dummy patterns on a photomask.

According to another aspect of the present invention, there is provideda semiconductor layout pattern having dummy patterns. The semiconductorlayout pattern includes a device layout pattern, a plurality ofrectangular first dummy patterns having a first size, and a plurality ofrectangular second dummy patterns having varied second sizes.

According to the dummy patterns and the method for generating dummypatterns provided by the present invention, the first dummy patternshaving the second density corresponding to the first density of thelayout pattern is formed in the layout region for preliminarilyequalizing the pattern densities in the layout region. Then, the layoutregion is divided into the sub-regions for checking sub-region bysub-region and thus the third density of each sub-region is obtained.Thereafter, the size of the first dummy patterns in each sub-region isadjusted according the difference between the third density and thesecond density. Therefore the pattern densities in each sub-region arefurther precisely adjusted. In other words, by adjusting the size of thefirst dummy pattern in each sub-region, the pattern densities, which areoriginally different from each other, of the sub-regions are smartlyadjusted and equalized. Accordingly, the sub-regions obtaining equalizeddensities are beneficial to the CMP process and improve the CMP result.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method for generating dummypatterns according to a first preferred embodiment and a secondpreferred embodiment of the present invention.

FIGS. 2-8 are drawings illustrating the method for generating dummypatterns according to the first and the second preferred embodiments,wherein FIG. 5 is an enlarged view of a portion of FIG. 4, FIG. 6 is aschematic drawing illustrating a modification to the preferredembodiments, and FIG. 8 is a simplified diagram of another modificationto the preferred embodiments.

FIGS. 9-10 are schematic drawings illustrating a third preferredembodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIGS. 1-8, wherein FIG. 1 is a flowchart illustrating amethod for generating dummy patterns according to a first preferredembodiment of the present invention, FIGS. 2-8 are drawings illustratingthe method for generating dummy patterns according to the firstpreferred embodiment, and FIG. 5 is an enlarged view of a portion ofFIG. 4. As shown in FIG. 1 and FIG. 2, the preferred embodiment firstperforms:

Step 10: Providing a Layout Region Having a Device Layout Pattern FormedTherein

It is well-known to those skilled in the art that an original circuitlayout patterns designed by the circuit design engineer is outputted ona photomask, and then transferred to an object layer by photolithographyand etching processes for producing a product that satisfies theelectrical function of the original circuit design. In the preferredembodiment, the layout region 100 includes a region on a photomask thatused to form layout patterns on an object layer, and FIG. 2 illustratesa portion of the layout region 100. The device layout pattern 110provided by the preferred embodiment includes the device layout patterndesigned by the circuit design engineer, such as interconnect layoutpatterns or circuit layout patterns, but not limited to this. Inaddition, the device layout pattern includes not only the efficientcircuit but also the dummy patterns (not shown) designed by the circuitdesign engineer. Please refer to FIG. 1, FIG. 2 and FIG. 5:

Step 12: Inserting a Plurality of First Dummy Patterns in the DeviceLayout Pattern

According to Step 12, a plurality of the first dummy patterns 120 isinserted in the device layout pattern 110. It is noteworthy that thefirst dummy patterns 120 include bar-like dummy patterns. And the firstdummy patterns 120 are positioned in between the device layout pattern110 or arranged to surround the device layout pattern 110discontinuously as shown in FIG. 2. Furthermore, a length of each firstdummy pattern 120 can be adjusted according to the spatial relationshipbetween the first dummy pattern 120 and the device layout pattern 110.In other words, each first dummy pattern 120 has a first size, and thefirst sizes are varied depending on the spatial relationship between thefirst dummy pattern 120 and the device layout pattern 110. As shown inFIG. 5, a spacing width a₁ is between the first dummy pattern 120 andthe device layout pattern 110. According to the preferred embodiment,the spacing width a₁ is exemplarily 0.2 micrometer (μm), but not limitedto this. It is noteworthy that the spacing width a₁ can be the minimumspacing width fulfills the design rule to the device layout patterns110. However a maximum of the spacing width a₁ can be smaller 2 μm.Furthermore, the first dummy patterns 120 can be single bar-likepatterns as shown in FIG. 2, but the first dummy patterns 120 still canbe multiple bar-like patterns that is preferably used in doublepatterning technology (DPT).

It should be easily realized that when forming a layout pattern in anobject layer, the contiguous areas between the iso region and the denseregion always bear greater stress due to the different pattern densitiesbetween the iso region and the dense region. It results serious defect,such as pattern distortion during the manufacturing process. To providea countermeasure against to the problems, the preferred embodimentpositions the first dummy patterns 120 substantially surrounding eachdevice layout pattern 110. The first dummy patterns 120 shield thedevice layout patterns from the stress, and thus pattern distortion isavoided.

Please refer to FIG. 8, which is a simplified diagram of a modificationto the preferred embodiment. Although only the first dummy patterns 120and the device layout pattern 110 are illustrated for emphasizing therelationship between the first dummy pattern 120 and the device layoutpattern 110 while other elements are omitted, it should be easilyrealize that other dummy patterns can be included in the modification.As shown in FIG. 8, the first dummy pattern 120 provided by themodification includes a close pattern that completely surrounding thedevice layout pattern 110 in a specific region. In addition, the firstdummy pattern 120 can be a single-line structure or a multi-linesstructure 120 a as shown in FIG. 8. Next, please refer to FIG. 1, FIG. 3and FIG. 5:

Step 14: Inserting a Plurality of Second Dummy Patterns in the DeviceLayout Pattern, and the Device Layout Pattern, the First Dummy Patternsand the Second Dummy Patterns have a First Density

According to Step 14, a plurality of second dummy patterns 130 isinserted in the device layout pattern 110. The second dummy patterns 130are arranged in an array in the layout region 100 as shown in FIG. 3 andFIG. 5. It is noteworthy that a spacing width b₁ is between a seconddummy pattern 130 that proximal to the device layout pattern 110 and thedevice layout pattern 110, a spacing width b₂ is between a dummy pattern130 that distal to the device layout pattern 110 and the device layoutpattern 110, and a spacing width b₃ is between each of the second dummypatterns 130. In the preferred embodiment, the spacing width b₁ islarger than or equal to 0.6 μm, spacing width b₂ is about 2.6 μm, andspacing width b₃ is between 90 nanometer (nm) and 210 nm. However, thespacing width b₁ and the spacing width b₂ can be adjusted according torequirement to the process or to the products. The spacing width b₃between each second dummy pattern 130 are also adjustable as long as aprecondition that no OPC is performed is met. The second dummy patterns130 are rectangular dummy patterns and preferably are square dummypatterns. As shown in FIG. 5, the second dummy patterns 130 include alength l₁ and a width w₁, which are between 240 nm and 360 nm. It isnoteworthy that the shapes and sizes of each second dummy pattern 130are all identical. In other words, the second dummy patterns 130 includefixed second sizes. Furthermore, an offset distance b₄ is existedbetween each second dummy pattern 130 along both of the X-direction andY-direction. In the preferred embodiment, the offset distance b₄ isbetween 0 nm and 300 nm, but not limited to this. It is also noteworthythat the device layout pattern 110, the first dummy patterns 120, thesecond dummy patterns 130 form a layout pattern, and the layout patternincludes a first density X.

It is well-known to those skilled in the art that after forming thelayout pattern in the object layer, specifically, after forming thetrench layout pattern of interconnects, a filling process is performedto fill the trench layout pattern with metal material. It is alwaysobserved that the filling speed in the iso region or at the edge of thedense region is much lower than the filling speed in the iso region.Consequently defect that the trenches are not filled up is found in theiso region or at the edge of the dense region. To provide acountermeasure against to the problems, the preferred embodimentpositions the second dummy patterns 130 substantially around the devicelayout pattern 110. Accordingly, pattern density in the iso region andat the edge of the dense region is increased, and thus a dense patternenvironment is formed around the device layout pattern 110. Thus thefilling speed in the iso region and at the edge of the dense region isincreased and the filling result of the filling process is improved.Then, please refer to FIG. 1, FIG. 4 and FIG. 5:

Step 16: Inserting a Plurality of Third Dummy Patterns with a SecondDensity

According to Step 16, a plurality of third dummy patterns 140 isinserted in the layout pattern (including the device layout pattern 110,the first dummy patterns 120 and the second dummy patterns 130). Thethird dummy patterns 140 are arranged in an array in the layout region100 as shown in FIG. 4 and FIG. 5. A spacing width c₁ is between a thirddummy pattern 140 that proximal to the device layout pattern 110 and thedevice layout pattern 110. In the preferred embodiment, the spacingwidth c₁ is larger than 3 μm, however the spacing width c₁ is adjustableaccording to requirement to the process or to the products. The thirddummy patterns 140 are rectangular dummy patterns, and preferably aresquare dummy patterns. As shown in FIG. 5, the third dummy patterns 140include a length l₂ and a width w₂, and the length l₂ and the width w₂are both between 460 nm and 740 nm. In addition, a spacing width c₂between each third dummy pattern 140 is between 160 nm and 440 nm. Anoffset distance c₃ is existed between each third dummy pattern 140 alongboth of the X-direction and Y-direction. In the preferred embodiment,the offset distance c₃ is between 100 nm and 600 nm, but not limited tothis. As shown in FIG. 4 and FIG. 5, the first dummy patterns 120 andthe second dummy patterns 130 are positioned between the third dummypatterns 140 and the device layout pattern 110, and the first dummypatterns 120 are positioned between the second dummy patterns 130 andthe device layout pattern 110.

It is noteworthy that the third dummy patterns 140 are positioned with asecond density Y, and the second density Y is corresponding to the firstdensity X. As mentioned above, the first density X is the density of thedevice layout pattern 110, the first dummy patterns 120 and the thirddummy patterns 130 according to the preferred embodiment. Therefore thethird dummy patterns 140 are positioned with the second density Ydecided according to the first density X as shown in Table 1:

TABLE 1 the first density X the second density Y X < 37.4% 34.8% 37.4% ≦X < 42.7% 40.0% 42.7% ≦ X < 48.5% 45.5% 48.5% ≦ X < 54.4% 51.3% 54.4% ≦X 57.6%

For example, when the first density X is larger than or equal to 37.4%and smaller than 42.7%, the second density Y is decided to be 40.0%.Accordingly the third dummy patterns 140 are positioned to have thesecond density Y of 40.0%. Furthermore, in the preferred embodiment, thesecond density Y serves as a target density set for the wholesemiconductor layout pattern. It should be noticed that though only 5ranges are provided by the preferred embodiment, more ranges andcorresponding target densities can be provided to further improveuniformity of the layout patterns. Please refer to FIG. 1 and FIG. 5,then Step 18 is performed:

Step 18: Dividing the Layout Region into a Plurality of Sub-Regions witha Third Density

According to Step 18, the layout region 100 is divided into a pluralityof sub-regions 1001, 1002, 1003 . . . 100 n. The sub-regions 1001, 1002,1003 . . . 100 n include identical length and width. For example, thelength and the width of the sub-regions are all 125 μm in the preferredembodiment. However the length and width of the sub-regions 1001, 1002,1003 . . . 100 n are not limited to this. As shown in FIG. 5. thesub-regions 1001, 1002, 1003 . . . 100 n may include the device layoutpattern 110, the first dummy patterns 120 and the second dummy patterns130, or include the second dummy patterns 130 and the third dummypatterns 140. The sub-regions 1001, 1002, 1003 . . . 100 n may includeonly the third dummy patterns 140. After obtaining the sub-regions 1001,1002, 1003 . . . 100 n, densities of each sub-region 1001, 1002, 1003 .. . 100 n are calculated and thus the third densities Z of eachsub-region are obtained. Since the sub-regions 1001, 1002, 1003 . . .100 n include 1 to 4 kinds of patterns, the third densities Z of thesub-regions have a large variation. In other words, there are manydifferences between the second density Y (the target density) and thethird densities Z of the sub-regions 1001, 1002, 1003 . . . 100 n.

In addition, please refer to FIG. 6, which is a schematic drawingillustrating a modification to the preferred embodiment. According tothe modification, the sub-regions 1001, 1002, 1003 . . . 100 n overlapto each other. Please refer to FIG. 1 and FIG. 7. Then Step 20 isperformed:

Step 20: Adjusting Sizes of the Third Dummy Patterns According to theDifference Between the Third Density and the Second Density

As mentioned above, since each third density Z of each sub-region 1001,1002, 1003 . . . 100 n is difference from the second density Y (thetarget density), the size of the third dummy patterns 140 in eachsub-region 1001, 1002, 1003 . . . 100 n are adjusted according to thedifference between the third density Z of individual sub-region and thesecond density Y. By adjusting the size of the third dummy patterns 140in each sub-region 1001, 1002, 1003 . . . 100 n, pattern density of eachsub-region 1001, 1002, 1003 . . . 100 n is consequently adjusted.Therefore the pattern densities of the sub-regions are equalized tosubstantially match the second density Y (the target density). In thepreferred embodiment, there are correlations between the second densityY, the third density Z and the size of the third dummy patterns 140 asshown in Table 2 and Table 3:

TABLE 2 The The The The The second second second second second densitydensity density density density The third Y = Y = Y = Y = Y = density Z34.8% 40.0% 45.5% 51.3% 57.6% 59.2% < Z o o m k i 56% < Z ≦ 59.2% o n lj h 52.8% < Z ≦ 56% o m k i g 49.9% < Z ≦ 52.8% n l j h f 47% < Z ≦49.9% m k i g e 44.1% < Z ≦ 47% l j h f d 41.3 < Z ≦ 44.1% k i g e c38.7% < Z ≦ 41.3% j h f d b 36.1% < Z ≦ 38.7% i g e c a 33.6% < Z ≦36.1% h f d b a 31.2% < Z ≦ 33.6% g e c a a 28.8% < Z ≦ 31.2% f d b a a26.6% < Z ≦ 28.8% e c a a a 24.5% < Z ≦ 26.6% d b a a a Z ≦ 24.5% c a aa a

TABLE 3 pattern density V of the adjusted size of the third dummypattern code sub-region (nm) a 60.80% 740 × 740 b 57.60% 720 × 720 c54.40% 700 × 700 d 51.30% 680 × 680 e 48.50% 660 × 660 f 45.50% 640 ×640 g 42.70% 620 × 620 h 40.00% 600 × 600 i 37.40% 580 × 580 j 34.80%560 × 560 k 32.40% 540 × 540 l 30.00% 520 × 520 m 27.70% 500 × 500 n25.60% 480 × 480 o 23.50% 460 × 460

For example, when the first density X is larger than or equal to 37.4%and smaller than 42.7%, the second density Y is decided to be 40.0%. Inan exemplar when the third density Z of the sub-region 1001 is largerthan 59.2%, a code “o” is obtained according to the table 2. The code“o” indicates sizes of the third dummy patterns 140 in the sub-region1001 are subsequently adjusted to have the length l₂ and width w₂ being460 nm according to the table 3. Accordingly, the pattern density V ofthe adjusted sub-region 1001 is lower to 23.50%, and thus the patterndensity of the sub-region 1001 is equalized. In another exemplar, whenthe third density Z of another sub-region 100 n is 24.5%, a code “a” isobtained according to the table 2. The code “a” indicates sizes of thethird dummy patterns 140 in the sub-region 100 n are subsequentlyadjusted to have the length l₂ and width w₂ being 740 nm according tothe table 3. Accordingly, the pattern density V of the adjustedsub-region 100 n is increased to 60.80%, and thus the pattern density ofthe sub-region 100 n is equalized. By adjusting the sizes of the thirddummy patterns 140 sub-region by sub-region, the pattern density of eachsub-region is adjusted to match the second density Y (the targetdensity). Accordingly, the density in the whole layout region 100 issubstantially equal to the second density Y. In other words, anequalized density is obtained. Please refer to FIG. 1 again. Thereafter,a Step 22 is performed:

Step 22: Outputting the Device Layout Pattern, the First Dummy Patterns,the Second Dummy Patterns, and the Third Dummy Patterns on a Photomaskto Form a Semiconductor Layout Pattern

According to Step 22, a semiconductor layout pattern includes the devicelayout pattern 110, the first dummy patterns 120, the second dummypatterns 130, and the third dummy patterns 140 is outputted on aphotomask and followed by performing necessary processes. The obtainedsemiconductor layout pattern has an advantage of superior uniformity. Itis noteworthy that in the semiconductor layout pattern, the first dummypatterns 120 include the varied first sizes, the second dummy patterns130 include the fixed second sizes, and the third dummy patterns 140include the varied third sizes. More important, the second sizes of thesecond dummy patterns 130 are smaller than the third sizes of the thirddummy patterns 140.

According to the first preferred embodiment, the first dummy patterns120 are positioned in the device layout pattern 110 and surround thedevice layout pattern 110 for shielding the device layout pattern 110from the stress caused by the different pattern densities between theiso region and the dense region. The second dummy patterns 120 arepositioned in the layout region 100 to form a dense region environmentfor increasing filling speed in the iso region and at the edge of thedense region, and thus the filling result of the filling process isimproved. More important, the preferred embodiment divides the layoutregion 100 into the sub-region 1001, 1002, 1003 . . . 100 n afterforming the third dummy patterns 140 and adjusts the sizes of the thirddummy patterns 140 in each sub-region according to difference betweenthe third density Z and the target density Y for smartly adjusting thepattern density of each sub-region to substantially match the targetdensity. Accordingly, the pattern density in the whole layout region 100is equalized and a semiconductor layout pattern having superioruniformity that is beneficial to the CMP process is obtained.Consequently, the CMP result is consequently improved.

Please refer to FIG. 1 again. FIG. 1 also illustrates a second preferredembodiment of the present invention. It is noteworthy that because mostof the steps performed in the second preferred embodiment are the samewith the first preferred embodiment, the same elements are designed bythe same numerals, and the same steps that are the Step 10-Step 22 areillustrated as shown in FIGS. 2-8. Therefore the details are all omittedin the interest of brevity. The difference between the second preferredembodiment and the first preferred embodiment is: In the secondpreferred embodiment, the Step 18 (dividing the layout region 100 intothe plurality of sub-regions 1001, 1002, 1003 . . . 100 n with differentthird densities Z) and the Step 20 (adjusting the size of the thirddummy patterns 140 according to the difference between the third densityZ and the second density Y) are taken as a cycle and repeatedlyperformed. In other words, the Step 18 and the Step 20 are periodicallyperformed.

It is noteworthy that the sizes of the sub-regions 1001, 1002, 1003 . .. 100 n in each cycle are different from other cycles. Therefore thethird density of the sub-regions 1001, 1002, 1003 can be different ineach cycle. And the sizes of the third dummy patterns 140 in eachsub-region are adjusted cycle by cycle, subsequently. Therefore thepattern density of each sub-region is adjusted many times in order tomatch the second density Y (the target density). Accordingly, byperforming the cycle having the Step 18 and Step 20, the patterndensities V of the adjusted sub-region 1001, 1002, 1003 . . . 100 n areoptimized and the whole pattern density in the layout region 100 isequalized to match the second density Y and a semiconductor layoutpattern having superior uniformity that is beneficial to the CMP processis obtained.

According to the second preferred embodiment, the first dummy patterns120 are still positioned for shielding the device layout pattern 110from the stress caused by the different pattern densities between theiso region and the dense region. The second preferred embodiment alsoprovides the second dummy patterns 120 positioned in the layout region100 to form a dense region environment for increasing filling speed inthe iso region and at the edge of the dense region, and thus the fillingresult of the filling process is improved. More important, the preferredembodiment periodically performed the Step 18 and Step 20, that is torepeatedly divide the layout region 100 into the sub-regions 1001, 1002,1003 . . . 100 n after forming the third dummy patterns 140 and torepeatedly adjust the third sizes of the third dummy patterns 140 ineach sub-region according to the difference between the third density Zand the target density after obtaining the sub-regions 1001, 1002, 1003. . . 100 n. By adjusting the sizes of the third dummy patterns 140 ineach sub-region repeatedly, the pattern densities in the sub-regions areoptimized and equalized. Accordingly, the pattern density in the wholelayout region 100 is equalized and a semiconductor layout pattern havingsuperior uniformity that is beneficial to the CMP process is obtained.Consequently, the CMP result is consequently improved.

Please refer to FIGS. 9-10, which are schematic drawings illustrating athird preferred embodiment of the present invention. It is noteworthythat because the third preferred embodiment is related to the thirddummy patterns 140 disclosed in the first and second preferredembodiments, only the third dummy patterns 140 are illustrated in FIGS.9-10 for descriptively illustrating and emphasizing the spatialrelationship between the preferred embodiment and the third dummypatterns 140. According to the third preferred embodiment, when thesemiconductor layout pattern provided by the first preferred embodimentand the second preferred embodiment is an interconnect layout patternwhich includes the first dummy patterns 120, the second dummy patterns130, the third dummy patterns 140 and the device layout pattern 110, andthe device layout pattern 110 includes trench patterns and dummypatterns designed by the circuit design engineer. Accordingly, the thirdpreferred embodiment provides a via layout pattern after forming theabove mentioned semiconductor layout pattern. The via layout patternincludes the via layout pattern designed by the circuit design engineer,the dummy patterns (not shown) designed by the circuit design engineer,and a plurality of via dummy patterns 150 for equalizing pattern densityof the via layout pattern. Furthermore, after forming the via dummypattern 150 in an object layer and filling the via dummy pattern 150with metal material, the filled via dummy pattern 150 is able to improvethe strength of the object layer, typically the low dielectric constant(low-k) material layer. As shown in FIG. 9, the via dummy patterns 150are rectangular dummy patterns, and preferably are square dummypatterns. A length l₃ and a width w₃ of the via dummy patterns 150 isbetween 72 nm and 180 nm. Furthermore the shapes and sizes of each thirddummy pattern 150 are identical.

More important, the via dummy patterns 150 are positioned correspondingto the third dummy patterns 140. As shown in FIG. 9, the via dummypatterns 150 are positioned corresponding to a center of each thirddummy pattern 140. Therefore the via dummy patterns 150 are positionedin a spatial range within the third dummy patterns 140 and overlappingto the third dummy patterns 140. In another exemplar, the via dummypatterns 150, as show in FIG. 10, are positioned along a diagonal lineof each third dummy pattern 140. Therefore the via dummy patterns 150are positioned in a spatial range within the third dummy patterns 140and overlapping to the third dummy patterns 140. Additional, the viadummy patterns 150 in different layer are arranged differently. Forexample, the via dummy patterns 150 in odd layer are arranged along adiagonal line 142 of the third dummy patterns 140 while the via dummypatterns 150 in the even layer are arranged along a diagonal line 144 ofthe third dummy patterns 140, and the diagonal line 142 and the diagonalline 144 are crisscross to each other.

According to the third preferred embodiment, the via dummy patterns 150are provided to improve strength of the low-k material layer of theinterconnect. It is noteworthy that the via dummy patterns 150 of thethird preferred embodiment are also positioned corresponding to thethird dummy patterns 140, specifically, the via dummy patterns 150 arearranged in a spatial range within the third dummy patterns 140 andoverlapping to the third dummy patterns 140. Because the third dummypatterns 140 are formed farther from the device layout pattern 110, thevia dummy patterns 150 formed corresponding to the third dummy patterns140 obtain a farther distance from the device layout pattern 110accordingly. In other words, a spacing width between a via dummy pattern150 proximal to the device layout pattern 110 and the device layoutpattern 110 is substantially the same with the spacing width c₁ thatbetween a third dummy pattern 140 proximal to the device layout pattern110 and the device layout pattern 110. The spacing widths are largerthan 3 μm.

Accordingly, when arrangement of the device layout pattern 110, thefirst dummy pattern 120, the second dummy patterns 130 and the thirddummy patterns 140 have to be changed due to requirement to product orprocess for forming the interconnects, the layout pattern of the viadummy patterns 150, which are farther from the device layout pattern110, still remain impervious and unchanged because the via dummypatterns 110 are not overlapped with the device layout pattern 110.Therefore cost and waste for reforming the layout pattern on a photomaskis economized. In other words, the via dummy patterns 150 provided bythe third preferred embodiment has the advantage that farther from thedevice layout pattern 110, thus a buffer area is obtained to avoidchanging to the via layout pattern even the corresponding layout patternhas to be changed.

In addition, according to the method for generating the dummy patternsprovided by the present invention, the semiconductor layout patternsobtained according to the first, second and third preferred embodimentsare outputted on a photomask, then, the semiconductor layout pattern canbe transferred into an object layer for performing processes necessaryto form the IC. In other words, the dummy pattern provided by thepresent invention includes not only the dummy patterns outputted on thephotomask, but also the dummy patterns transferred to the object layer.

Furthermore, the second dummy patterns 130 and the third dummy patterns140 formed in different layers includes a predetermined relativearrangement. For example, the second dummy patterns 130 are arranged ina spatial range within the third dummy patterns 140 and overlapping tothe third dummy patterns 140, but not limited to this. Due to thespecial relative arrangement for the second dummy patterns 130 and thethird dummy patterns 140, reduction of parasitic capacitance isoptimized.

As mentioned above, according to the dummy patterns and method forgenerating the dummy patterns provided by the present invention, thethird dummy patterns having the second density (the target density)corresponding to the first density of the layout pattern is formed inthe layout region for preliminarily equalizing the pattern densities inthe layout region. Then, the layout region is divided into thesub-regions for checking sub-region by sub-region and thus the thirddensity of each sub-region is obtained. Thereafter, the size of thethird dummy patterns in each sub-region is adjusted according thedifference between the third density and the second density. Thereforethe pattern densities in each sub-region are further precisely adjusted.In other words, by adjusting size of the third dummy patterns in eachsub-region, the pattern densities, which are originally different fromeach other, of the sub-regions are smartly equalized. Accordingly, thesub-regions obtaining equalized densities are beneficial to the CMPprocess and thus improve the CMP result. Additionally, the dummypatterns and method for generating the dummy patterns provided by thepresent invention, also improves other process result such as theetching result of the patterning process.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention.

What is claimed is:
 1. A method for generating dummy patterns comprisingsteps of: providing a layout region having a layout pattern with a firstdensity; inserting a plurality of first dummy patterns with a seconddensity corresponding to the first density in the layout pattern;dividing the layout region into a plurality of sub-regions, eachsub-region comprising a third density; adjusting a size of the firstdummy pattern in each sub-region according to a difference between thesecond density and the third density; and outputting the layout patternand the first dummy patterns on a photomask.
 2. The method forgenerating dummy patterns according to claim 1, wherein the layoutpattern comprises at least a device layout pattern, a plurality ofsecond dummy patterns and a plurality of third dummy patterns.
 3. Themethod for generating dummy patterns according to claim 2, wherein thedevice layout pattern comprises interconnect layout patterns or circuitlayout patterns.
 4. The method for generating dummy patterns accordingto claim 2, wherein the second dummy patterns and the third dummypatterns are sequentially inserting in the device layout pattern beforeforming the first dummy patterns.
 5. The method for generating dummypatterns according to claim 2, wherein the second dummy patternscomprise bar-like dummy patterns and the third dummy patterns compriserectangular dummy patterns.
 6. The method for generating dummy patternsaccording to claim 2, wherein the second dummy patterns comprise variedsizes and the third dummy patterns comprise fixed sizes.
 7. The methodfor generating dummy patterns according to claim 6, wherein the thirddummy patterns are smaller than the first dummy pattern.
 8. The methodfor generating dummy patterns according to claim 1, wherein thesub-regions overlap each other.
 9. The method for generating dummypatterns according to claim 1, further comprising repeatedly performinga cycle having the steps of dividing the layout region into thesub-regions with the third density and adjusting the size of each firstdummy pattern according to the difference between the third density andthe second density.
 10. The method for generating dummy patternsaccording to claim 9, wherein sizes of the sub-regions are different ineach cycle when performing the step of dividing the layout region intothe sub-regions with the third density region.